I still don't see what distinction you're making from the content of what you say, but since you say you've made the distinction, sure, I'll address the points as best as I can. Keep in mind that everything I say is about what evolutionary psychology has the principle to be. If you respond with "but so-and-so has this really dumb theory about sexual orientation that totally contradicts what you said," then I am simply going to point out that that's an Xa-type complaint and is irrelevant.

What's my personal definition? The canonical one, in full generality.

The journal Evolutionary Psychology says: "Evolutionary Psychology (EVP) is an open access, peer-reviewed journal which focuses on original, empirical research addressing human psychology guided by an evolutionary perspective."

The Evolutionary Psychology section of Frontiers in Psychology says: "This specialty section accepts articles across the spectrum of evolutionary psychology and related fields (e.g., animal behavior; biological, physical, and psychological anthropology, evolutionary biology) that take an evolutionary approach to understanding human and non-human behavior."

Wikipedia says: "Evolutionary psychology is a theoretical approach in psychology that examines cognition and behavior from a modern evolutionary perspective. It seeks to identify human psychological adaptations with regards to the ancestral problems they evolved to solve."

The Standford Encyclopedia of Philosophy says: "What distinguishes evolutionary psychologists from many cognitive psychologists is the proposal that the relevant internal mechanisms are adaptations—products of natural selection—that helped our ancestors get around the world, survive and reproduce."

That all sounds good to me.

I do not endorse all of Tooby and Cosmides' tenets (e.g. as conveyed at https://plato.stanford.edu/entries/evolutionary-psychology/#EvoPsyTheMet) for how they envision evolutionary psychology working in practice, though they're not too terrible. The reason I don't endorse them is that although some of the tenets are reasonable places to start, you can abandon almost all of them and yet still be wholly taking an evolutionary approach to understanding human psychology. (For instance, the "cognitive modules" stuff makes things a bit more concrete when trying to isolate evolutionary effects, but if it turns out cognitive modules are a bad way to conceptualize cognition, they can be replaced with a better model. )

There are ways that evolutionary psychology as an entire field of study could be falsified.

For instance, if we were able to show that genes did not affect human behavior or cognition, either individually or in combination, then it would be falsified: it just doesn't work that way.

Alternatively, if we were able to show that humans did not evolve, evolutionary psychology would be dead. Likewise, if we could show that humans didn't have psychology. Or if we could show that although humans evolved and genes did affect psychology, the impact on fitness was too small to be an important factor in fixing alleles or strongly sculpting their frequencies.

However, we have exceedingly good evidence that genes do affect human behavior and cognition (with separated twin studies leading the way), so the foundations for the attempt seem highly secure. Pointing out that genes aren't everything is no more relevant than pointing out that smoking isn't everything for cancer: genes matter too. Okay! Multiple causal factors. Got it. That's how complex systems usually work. Nothing surprising about that! Noting that there are multiple causal factors doesn't stop us from studying how smoking promotes lung cancer.

(Likewise, pointing out that there is considerable variability in behavior, or in cancer, doesn't stop us from studying behavior, or cancer, including the variability as needed.)

Where evolutionary psychology is on less secure footing is the hope that the evolutionary pressures are knowable, and that the impact of those pressures have comprehensible impacts on cognition. Although the theory isn't overturned if we can't discern the original pressures with any fidelity, it considerably reduces the utility, because all our reasoning has to go from observations now into speculations about the past. We could, alternatively, just make observations now and not speculate about the past. Unless you can get back to the present again, noting that something-or-other in the past may or may not have selected for this or that trait in some form or another is so wishy-washy as to be pointless.

This is definitely a way evolutionary psychology could fail, and it would be an Xb problem not an Xa problem, because the danger is that there is no extra information to be had: the premises are fine, but the key causal factors cannot be determined, either directly or by working backwards from what we observe about human psychology, and without those the theory makes no substantive predictions.

However, here too, things seem promising--but maybe not nearly of the scope that practicing evolutionary psychologists would like. There are certain evolutionary pressures that are nearly universal--for instance, the necessity to avoid freeloading--and although the predictions that one can make in the absence of details are necessarily somewhat limited, one can potentially understand more than nothing. So unless it is the case that traits like honesty and vigilance for dishonesty are unmoved by genetic variation, it does not seem that there's any plausible way for there to be literally nothing for evolutionary psychology to do.